Valve structure

ABSTRACT

A valve of the type which is actuated under the pressure of the medium it controls and in which axially-aligned actuating and damping pistons are disposed within cylindrical relief and damping chambers and are connected to a valve element engageable with a valve seat disposed between inlet and outlet valve ports. The actuating piston acts under the pressure of the medium it controls to actuate the valve element in response to a reduction in pressure in the relief chamber. The invention itself resides in the provision of a restricted passageway which interconnects the relief and damping chambers whereby the pressure in the damping chamber will be reduced slowly in response to a reduction in pressure in the relief chamber whereby, if the valve should stick or otherwise become slow-acting, the pressure within the damping chamber will assist and insure that the valve is actuated even though it may not be in the best operating condition.

BACKGROUND OF THE INVENTION

As is known, ON-OFF valves for compressible fluid media have beenprovided in the past which are actuated by the pressure of the fluidthey control, the valve spool being connected to an actuating pistonmovable within a cylindrical relief chamber and to a damping piston,usually coaxial with the actuating piston, reciprocable in a cylindricaldamping chamber. The actuating piston is subjected to the pressure ofthe compressible medium controlled by the valve to actuate the valve inresponse to a reduction in pressure in the aforesaid relief chamber inwhich the actuating piston reciprocates.

Various constructions of valves of this type are known. They are used aseither quick-closing valves serving to shut off sections of a pipelinein the event of dangerous operating conditions arising, such as linebreaks or the like, or as quick-opening valves responding to excesspressure. Forces for actuating the valve can be produced by an actuatingpiston which experiences either the pressure of the flow medium itselfor a reduction in such pressure.

Since valves of this type are primarily used for safety purposes, theymust be very reliable in operation. It is for this reason that suchvalves are often of a size and design to insure that the forces whichactuate them are much larger than necessary so that the valve operatessatisfactorily even when the valve spool or the like has a tendency tostick or becomes difficult to move for any reason once the valve hasbeen in use for a period of time.

SUMMARY OF THE INVENTION

It is an object of the present invention to insure that in the eventthat a valve of the type which has a tendency to stick or otherwisebecome difficult to move after a period of time, additional forces willautomatically become effective to enhance the normal valve operatingforce and thus make it possible for the valve to operate underconditions where it might not otherwise operate under conditions whereit might not otherwise operate after an extended period of use.

In accordance with the invention, a valve is provided of the type inwhich axially-aligned actuating and damping pistons are disposed withincylindrical relief and damping chambers, respectively, and are connectedto a valve element engageable with a valve seat disposed between inletand outlet valve ports. Typically, the actuating piston, the dampingpiston and the valve element, comprising the valve spool, are coaxialand housed within a common valve body. Forces exerted on the valve spoolby the fluid within the relief and damping chambers are equalized undernormal operating conditions. However, by reducing the pressure in therelief chamber, the valve can be actuated to assume either an open orclosed condition, depending upon the particular design of the valve. Inthe usual case, the pressure within the damping chamber remainsrelatively constant when the valve is actuated, actuation of the valvebeing totally dependent upon a reduction in pressure in the reliefchamber. A restricted passage, however, interconnects the relief anddamping chambers such that, while the pressure in the damping chamberwill not be reduced during a normal valve actuation, it will be reducedslowly and will assist in the valve actuation in the event of a stickingor otherwise difficult-to-operate valve condition. In this manner, andin the event of sticking or otherwise unsatisfactory operation of thevalve when the normal actuating forces cannot move the spoolsatisfactorily, the damping chamber is used as an additional reliefchamber (i.e., the effective surface area presented to the fluid mediumis increased by the effective surface area of the damping piston, inaddition to that of the actuating piston). Appropriate dimensioning ofthe restricted passageway assures that the damping chamber will comeinto operation as an additional relief chamber only when the valve hasfailed to operate after the normal actuation time period.

In an advantageous embodiment of the invention, the damping piston andrelief piston are coaxial, stepped pistons, the damping piston being oflarger diameter than the relief piston, and the damping chamber beingseparated from the relief chamber by a sealing element in the form of apiston ring disposed on the periphery of the relief piston. A secondpair of piston rings surrounds the damping piston to form an annular gapwhich is connected to the relief chamber through the aforesaidrestricted passageway. The provision of a direct connection from theannular gap between the aforesaid piston rings on the damping piston tothe relief chamber insures that high-pressure fluid will not betransferred from the high-pressure side of the valve to the dampingchamber, a condition which would inhibit the required pressure relief ofthe damping chamber. The invention can be carried into effect in a valvehaving substantially leak-free piston rings or one in which the pistonrings permit a certain amount of leakage, depending upon requirements.

Preferably, the aforesaid restricted passageway connecting the reliefand damping chambers incorporates a variable restriction, whereby flowthrough the restriction can be controlled as well as the operating timeof the valve.

The above and other objects and features of the invention will becomeapparent from the following detailed description taken in connectionwith the accompanying drawings which form a part of this specificationand in which:

FIG. 1 is a cross-sectional view, in elevation, of one embodiment of theinvention wherein the valve is a quick-closing valve; and

FIG. 2 is an elevational cross-sectional view of another embodiment ofthe invention wherein the valve comprises a quick-opening valve.

With reference now to the drawings, and particularly to FIG. 1, thevalve shown includes a valve body or casing 1 and an upper cover 2 whichis secured to the main valve body 1 by means of screws or bolts, notshown. Depending downwardly from the cover 2 is a cylindrical valveinsert 3 which receives the valve operating elements about to bedescribed.

Formed in the insert 3 is upper or first cylindrical cavity 4 and acommunicating lower cylindrical cavity 5 at a smaller diameter. Thebottom termination of the insert 3 is in the form of a projection havinga surface 6 adapted to abut the upper periphery of a valve element 7.When the valve is in a closed position, a sealing surface on valveelement 7 engages annular valve seat 8 formed in the body 1.

Valve element 7 is part of a valve spool which includes actuating piston9 coaxial with and connected to a larger diameter damping piston 10.Piston 9 is reciprocable within the cylinder 5 and is surrounded bypiston ring 11 which abuts the walls of the cylinder 5. The piston ring11 separates two operating chambers (i.e., the relief chamber 12 anddamping chamber 13) one from the other but at the same time can permit acertain amount of leakage from one chamber to the other.

In a similar manner, the piston 10 is provided with two spaced pistonrings 14 separated by an annular gap between the periphery of the pistonand the periphery of chamber 4. A passageway 15 of restricted crosssection is formed in the adjoining pistons 9 and 10 and extends from theannular gap formed between the piston rings 14 to the relief chamber 12.Projecting upwardly from the upper surface of the piston 10 is acylindrical projection 16 which terminates in a flanged portion 17. Ahelical compression spring 19 is disposed between flange 17 and annularshoulder 18 formed in the cover 2 and acts to hold the valve element 7in an open position wherein it is separated from the valve seat 8.

The valve body 1 is provided with a valve inlet port 23 and a valveoutlet port 24 between which is the valve seat 8. Auxiliary lines whichextend from the inlet port 23 and the outlet port 24 are shown in brokenlines in the drawing and are connected to a bore 25 in the cover 2.These auxiliary lines or conduits insure that the space above thedamping piston is filled with the medium controlled by the valve at themaximum operating pressure. Check valves 26 in the auxiliary conduitsinsure that, when the valve is in a closed condition, there can be notransfer of fluid from the inlet port 23 to the outlet port 24.

Formed in the outer wall of the valve insert 3 is a discharge duct 20which communicates with the relief chamber 12 and is connected at itsother end through control valve 21 to a low pressure conduit 22. Thepassageway 15 formed in the pistons 9 and 10 is connected through atransverse duct 27 to the damping chamber 13. In this way, it will beappreciated that the damping chamber 13 and the relief chamber 12 are incommunication with each other. Preferably, the duct 27 is provided witha variable restriction, not shown, which enables the issuing quantity offluid medium to be varied as well as the closing time of the valve.

Operation of the valve shown in FIG. 1 is as follows: When the valve isopen, all of its internal chambers are accessible to the flow medium andare at the pressure existing at the valve inlet 23. This occurs, asregards chambers 12 and 13, by virtue of a certain amount of leakagearound the piston rings 11 and 14 as explained above. In order to closethe valve, the control valve 21 is opened, thereby reducing the pressurein the relief chamber 12. Under these conditions, the upward force onthe valve spool is less than the downward force exerted by the fluidpassing into the valve body through port 25. As a result, the valvespool including valve element 7 are moved rapidly from an openedposition to a closed position. The closing operation is damped since themovement of the damping piston reduces the volume of the compressiblemedium in the damping chamber 13. When the valve is in proper workingorder, and because of the relatively short actuation time, there is noappreciable relief of the damping chamber via the passageway 15 duringnormal operation.

On the other hand, if the valve has become difficult to move after aprolonged period of operation, such that the closing force arising fromthe normal pressure difference is insufficient to actuate the valve,fluid will be transferred from the damping chamber 13 to the reliefchamber 12 via the clearance around the piston ring 11 and via the bore27 and duct 15. As a result, the pressure in the damping chamber 13drops slowly but surely to the pressure in relief chamber 12. Thedifferential force acting to close the valve correspondingly increasesand causes the valve to close. This feature insures that sufficientreserves of closing force are present when, after prolonged operation,the spool valve does not move as readily as previously.

The size and design of the duct passageway 15 is such that after thevalve 21 has opened, pressure in the annular gap between the pistonrings 14 decreases to the pressure in the relief chamber 12, such thatfluid cannot pass from the chamber above the damping piston 10 intodamping chamber 13 in normal operation, nor in conditions of operationof reduced effectiveness.

The bore 27, which comprises a restriction of variable cross section asdescribed above, provides a means for controlling the time for pressureequalization between the damping chamber and the relief chamber 12 whenthere is a tendency of the spool valve to stick and in addition, it cancontrol the speed of closure during normal or abnormal conditions ofoperation.

FIG. 2 shows another embodiment of the invention as applied to aquick-opening valve. Since many of the elements in FIG. 2 correspond tothose of FIG. 1, they are identified by like reference numerals.Operation as regards adding the damping chamber 13 as a relief chamberin order to increase the actuating force (which in the case of FIG. 2 isthe opening force) is the same as for the quick-closing valve shown inFIG. 1. That is, when the valve element or spool tends to stick, fluidfrom damping chamber 13 flows to the relief chamber defined by thecylinder 5 through restriction 27 and through the valve 21. As in theembodiment of FIG. 1, the restricted orifice 27 comprises a means forvarying the opening time for the quick-opening valve of FIG. 2. Asidefrom this, the relationship between the operative surfaces of thestepped piston and spool arrangement in FIG. 2 is the same as that inFIG. 1 in that adequate opening force reserves are available, thusassuring that the valve can operate reliably even though it is not inparticularly good operating condition.

Although the invention has been shown in connection with certainspecific embodiments, it will be readily apparent to those skilled inthe art that various changes in form and arrangement of parts may bemade to suit requirements without departing from the spirit and scope ofthe invention.

I claim as my invention:
 1. An on/off valve for use with compressiblefluids, actuated by the fluid which it controls, said valve includingaxially aligned first and second chambers;a first piston in said firstchamber; a second piston in said second chamber; said first and secondpistons being mounted on a common valve spool; said first chamber andsaid first piston defining an operating chamber; said first chamber andsaid first piston defining an annular damping chamber about said secondpiston; said second chamber and said second piston defining a reliefchamber; operating means for said valve comprising a valved fluidpassageway extending from said relief chamber to permit reduction offluid pressure in said relief chamber; a first fluid passageway in saidvalve spool directly connecting said damping chamber and said reliefchamber to permit the pressure in said damping chamber to be slowlyreduced in response to a reduction in pressure in said relief chamber;at least two axially-spaced piston rings between said first piston andsaid first cylinder, and including a second fluid passageway throughsaid valve spool connecting the space between said piston rings to saidrelief chamber whereby fluid from the operating chamber may leak intothe relief chamber, and resilient means acting on the first piston tomaintain the valve in a normally open position and means for introducingthe highest fluid pressure into the operating chamber from the valveinlet or outlet.
 2. A normally open on/off valve for use withcompressible fluids, actuated by the fluid which it controls, said valvehaving axially aligned first and second communicating cylinders;a firstpiston in said first chamber; a second piston in said second chamber;said first and second pistons being carried on a common valve spool;said valve spool extended through said second chamber to terminate in avalve element and extended through said first chamber to terminate in aprojection; resilient means for urging said projecting away from saidfirst chamber; said first chamber defining an annular damping chamberbetween the said first piston and the center of said valve and furtherdefining an operating chamber between said first piston and saidprojection; leakage means for said fluid from said operating chamberpast said first piston into said annular damping chamber; said secondchamber defining an annular relief chamber between said second pistonand said valve element; a fluid inlet and a fluid outlet; valve seatmeans opposing said valve element between said inlet and said outlet;unidirectional fluid passageways for introducing said fluid from saidinlet to said operating chamber and from said outlet to said operatingchamber, whereby the highest fluid pressure from said unidirectionalfluid passageways enters said operating chamber enlarging the saidoperating chamber and advancing the said valve spool toward said valveseat means to close said valve; a fluid bleed passageway extending fromsaid relief chamber outside said valve for releasing the fluid from saidrelief chamber and for closing said valve element; a damping fluidpassageway within said valve spool directly connecting said dampingchamber and said relief chamber to permit the pressure in said dampingchamber to be slowly reduced in response to a reduction in pressure insaid relief chamber.
 3. The improvement of claim 2 wherein the saiddamping fluid passageway has a variable restriction within said valvespool to vary the speed of operation of said valve.